Wonder Girl is a very tough young girl, with a very energetic, carefree and eager personality. In general, she prefers taking on foes stronger than herself. She loves to fight, and enjoys missions in which there will be physical confrontations. Sitting on the sidelines is less to her liking.
She can occasionally lose focus when impressed by something, but can regain focus when corrected. Her teammates have also remarked that stealth is not her strong suit.
Wonder Girl has a slender yet muscular build with blue eyes and blonde hair with unkempt bangs. Her hair is long, running down her back, and she wears a black headband. She wears a black sleeveless top with two stylized golden W's on it, which resemble the W's that Wonder Woman wears across her camisole. She has red pants with two white stripes on the sides, and blue shoes. When her Stealth-tech is active, her entire costume, shoes and all, turns black, with the exception of the stylized W's, which turn gray.
Like Wonder Woman, she wears two silver bracelets and star earrings (though silver instead of red, unlike her original designs), and uses a golden lasso that hangs at her waist.
By 2020, she had received an upgraded suit with more details. She now wore a sleeveless jumpsuit top with a red section resembling her mentor's new costume, but with a black section covering her chest. She wears matching black undersleeves with fingerless gloves with a white star on the back of her hand. With red pants and her boots are now red as well and extend above her knees, with golden kneepads. In addition to her lasso, she now wears a golden belt.
Cassie is the daughter of Helena Sandsmark and the Greek god Zeus. She was raised by her single mother, though she was often left on her own when her mother went on archaeological expeditions.
On the way to their target, Wonder Girl explained she was excited about being on Alpha Team with him. Nightwing empathized, and told her of his early days on the Team. He also explained why he chose Cassie to come with: they were recruiting a new member, and as she was still new to the Team, she could be vital.
El Paso December 1, 08:19MST
On the roof of the Rio Grande High School, Nightwing quickly went through their data on Blue Beetle with her, before sending her to meet Jaime Reyes, the Blue Beetle. Nightwing figured that sending a girl would reduce the chance of the meeting ending in a fight.
Cassie moved in and surprised Jaime, even more so because she explained she wanted to talk about Blue Beetle. Nightwing then joined the conversation, and offered their friendship.
El Paso December 1, 08:29MST
Their conversation with Jaime was cut short when the Watchtower contacted Nightwing. While he conferenced with the Watchtower and the Cave, Wonder Girl kept Jaime from interfering.
El Paso December 1, 08:32MST
Nightwing and Wonder Girl discussed what to do next. Cassie was especially upset that she wasn't abducted along with Wonder Woman, as Superboy did disappear. Jaime wanted to excuse himself, but Nightwing insisted that he'd consider. He told him that Ted Kord was a friend of his, and he would've wanted him to join.
El Paso December 1, 08:42MST
Cassie tried convincing Jaime by telling him how the Team had helped develop her skills and powers, but Jaime was still hesitant. He wanted to discuss it with Peacemaker, Green Lantern and Captain Atom, but all were unavailable. Their conversation was cut short by another emergency, this time in Metropolis. Nightwing asked Jaime if he would like to come along.
New Mexico December 1, 09:00MST
Alpha Squad took the Super-Cycle to Taos, with Blue Beetle in tow.
Alpha Squad arrived at Metropolis. After they landed, a number of Justice League members reported on their failure to penetrate the force field surrounding the city. Despite the bad news, Wonder Girl understood Blue Beetle's excitement at the events.
As Martian Manhunter and Flash attempted to communicate with the alien ship over Metropolis, Wonder Girl, Nightwing, Blue Beetle, and Zatanna hovered nearby on the Super-Cycle, concealed inside a magic glamour bubble.
Metropolis December 1, post-17:54EST
Alpha Squad successfully entered the Collector of Worlds's ship through a hatch that was opened to expel Martian Manhunter, Flash and Atom.
Metropolis December 1, 18:20EST
Alpha made its way through the inner corridors of the vessel. Blue Beetle, still star-struck, engaged in a conversation with Zatanna. She revealed information about the Team and Nightwing to him, which led Cassie to conclude she had blown his mind.
Nightwing cut short the conversation, as he stumbled upon a room full of spheres. From a distance, Blue Beetle thought they were dioramas, but Nightwing discovered they were actually shrunk down cities.
Metropolis December 1, 18:31EST
They continued on, planning to return for the shrunken cities later. But as they walked, Zatanna noticed her glamour was fading. Before she could put up a new one, the Collector of Worlds ambushed and stunned them.
Wonder Girl was still knocked out. Blue Beetle and Sphere managed to counterattack.
The Collector's Ship December 1, 19:01EST
Alpha Squad regrouped and attacked the Collector, but the alien put up a forcefield. Just then, those who were on Kylstar's vessel were teleported in, as well as the Flash, Atom and Martian Manhunter, and they made quick work of the alien.
Metropolis December 1, 19:03EST
The heroes and villains were cornered by dozens of new coludroids. Wonder Girl watched as Nightwing and Captain Atom persuaded the Collector to cease his attack.
Metropolis December 1, 22:03EST
With Metropolis restored to full size, the heroes gathered in the park. Wonder Girl met up with Blue Beetle, and asked him if he had made up his mind. He had, but he had to convince his scarab he was going to join.
When Lobo was trying to kill secretary general Tseng, Wonder Girl and Batgirl were called in, and distracted the alien. Batgirl tried to escape with Tseng, while Wonder Girl took care of Lobo. Lobo eventually prevailed and revealed that Tseng was a robot, operated by a Krolotean. Lobo left with the Krolotean, as Wonder Girl looked on.
After the Justice League identified locations around the world with Krolotean activity, Wonder Girl was assigned as Alpha Squad along with Nightwing, to capture the remaining Kroloteans in Philadelphia.
Wonder Girl and her mentor, Wonder Woman, were part of Delta Squad during the mission to stop the Kroloteans on Malina Island. They were called in for backup when the enemies started to retreat. They both took out multiple Mechs. When they learned the base was set to explode, they picked up Aquaman and Lagoon Boy and retreated to the Bio-Ship.
As the Leaguers accused of crimes on Rimbor prepared to depart, Wonder Girl expressed her desire to come along. Wonder Woman refused, as only a select group would be necessary, and she could never convince her mother to allow it.
Aboard the Bio-Ship on her way to a mission to Bialya with Miss Martian, Bumblebee, and Batgirl, Wonder Girl was briefed by Nightwing, though she already knew what the mission details were. She laughed with the other girls after Batgirl called Nightwing out on why he had to justify choosing an all girl team.
Wonder Girl was upset when Miss Martian ordered her to stay behind as a lookout while the other three girls infiltrated the base. After protesting briefly, she accepted the instruction. Wonder Girl watched the three girls enter the base, before spotting a truck carrying Mammoth, Icicle Jr., Devastation, Shimmer, and Psimon, who was previously thought to be hospitalized. Realizing she couldn't contact her teammates without Psimon knowing they were there, she had to warn them by finding them in the base.
After finding Miss Martian, she set out to warn the others, but was discovered by Devastation, who pinned her down. She fought her and several Bialyan soldiers off, and made it to the rendezvous point. They were later joined by Bumblebee, who notified them of Batgirl's capture. They set out to liberate her, and the abductees she had found.
Wonder Girl stayed in reserve while the others rescued Batgirl. She forced open a gate where Batgirl could fly a plane with all the abductees through, and made sure Devastation couldn't get to her. Unfortunately, the plane was damaged, and without its wings, fell off the end cliff at the end of the runway. Wonder Girl tried to lift it up, but it was too heavy. However the Bio-Ship saved them both.
Cassie was disappointed their mission gave them so many unanswered questions, but Nightwing assured her that it was a success nonetheless. The other girls congratulated Wonder Girl on her successful mission with a group hug.
Cassie attended Raquel Ervin's bridal shower with all the other female members of the Justice League and the Team. After the party was interrupted by an armored car robbery by Captain Cold, Cassie assisted in his defeat.
After Alpha Squad infiltrated the Manta-Flyer in Star City, Nightwing, Miss Martian and Wonder Girl followed it discreetly in the Bio-Ship. She asked Nightwing how he knew about the new abduction and how he could know it would lead them to Lagoon Boy, to which he answered that Aquaman found the intel, and it was part wishful thinking.
They got close to their target, an underwater base. While Nightwing noted it was similar to the bombs, it reminded Cassie of Blue Beetle's armor. Miss Martian went in, and she and Alpha Squad liberated the captives. Wonder Girl stewarded the door as the Bio-Ship docked, and she oversaw the evacuation.
The operation was cut short by a Reach enforcer, who locked the bay doors. Wonder Girl threatened him and warned him he was outnumbered, and dubbed him "Black Beetle" in the process. The Black Beetle proved the superior warrior, though Cassie managed to land several futile punches before she was thrown aside. But she would not give up; she charged him with Superboy. It did not help. She contacted Nightwing for help, and squared off with the Black Beetle again. He pinned her down against the door, and mercilessly slammed her into it until she was down. Blue Beetle, Beast Boy, and Impulse arrived, and while Blue Beetle held off the Black Beetle, Impulse helped Cassie aboard the Bio-Ship. There, she was fit enough to look after Superboy.
Wonder Girl joined other Team members in secretly boarding the Warworld, a giant satellite controlled by the alien despot Mongul. She was part of Alpha Squad with Superboy, Arsenal, and Wolf, whose objective was to take down Mongul. Alpha Squad first had to battle drones that protected Warworld before confronting Mongul. The alien despot proved too powerful for them to take down, but after Bumblebee created a power surge to stun Mongul, Alpha Squad was able to subdue him.
The Warworld May 26, post-12:40UTC
Alpha Squad joined the rest of the Team in the docking bay, having taken longer to get there because of how heavy Mongul was. As Wonder Girl and Superboy carried Mongul, Arsenal watched as Bumblebee and Guardian shared a kiss and wondered how he might get one. Wonder Girl then gave Arsenal a peck on the cheek. Blue Beetle then suddenly hit Impulse with the crystal key he had retrieved and attack the rest of the Team. Superboy was knocked aside and Wonder Girl was trapped underneath Mongul and pinned down by Beetle with a staple. After Arsenal panicked and opened the airlock, Beetle was able to close it and take down the rest of the Team, except for Arsenal, who escaped.
The Warworld May 30, post-03:36UTC
Wonder Girl and the rest of the Team were held in stasis chambers as prisoners of the Reach. Arsenal, along with four teens that the Team had rescued from the Reach's underwater base, ultimately freed the captured Team members.
While Zatanna was preparing a ritual to prevent the Reach from controlling Blue Beetle, Green Beetle arrived to try and free him. Batgirl and Impulse tried to stop him, but did not succeed and were knocked out. Luckily, Wonder Girl, Robin, Bumblebee, and Beast Boy intervened. Wonder Girl lassoed him, while Robin attacked him with a flying kick. They managed to keep him preoccupied until Zatanna completed the incantation, and returned control of their bodies to Green Beetle and Blue Beetle.
When magnetic field disruptors planted by the Reach threatened the Earth, Wonder Girl joined 39 other heroes of Earth in a briefing in Metropolis City. The heroes would use a computer virus provided by Lex Luthor to safely disable the disruptors. The heroes were paired off with another into twenty squads: one member would run interference against weapons guarding the disruptors, allowing the other to get close enough to plant the virus. When Wonder Girl expressed her incredulity at their working with Lex Luthor, Robin told her it wasn't in Luthor's best interest for Earth to be destroyed; at any rate, they don't have any other alternative.
Wonder Girl was assigned to Tau Squad, and worked alongside Robin. Within thirty minutes, all squads had succeeded in their mission.
Tim and Cassie welcomed Static to the Team, and inquired about the whereabouts of his former teammates. Unbeknownst to Static but noticed by Superboy, the pair were holding hands behind their backs. After Wally's death, they had become a couple after she gained enough nerve to kiss him. Aqualad summoned everyone to the mission room, where Batman informed the Team that they would now operate side by side with the Justice League from the Watchtower. Not because Mount Justice was destroyed, but because they earned the right to do so. Aqualad assigned Wonder Girl to Gamma Squad to investigate Batgirl's lead about the whereabouts of Vandal Savage.
The Team's latest debriefing coincided with a Justice League meeting. As they had already finished, Wonder Girl chatted with Robin when the League meeting was broken up. Only Batman and Green Arrow came out of the conference room and summoned their protegés with them. Cassie was shocked Tim left without as much as a word.
Bear's mission for the Team involved investigating an alleged assault by Orion during a trade deal with bugs. Cassie was quick to dismiss the need for Robin's detective skills, as she just came off a conversation in which he showed none of them. The bug leader Mantis cooperated and they set up another deal.
Cassie was baffled when mid-deal, Miss Martian suddenly reverted to her Martian form and dragged Orion away. The Team followed and fought "Orion"'s meta-human slaves Blister and Giant. Wonder Girl and Static took down the malleable Giant. The bugs turned on them, but one of their number, Forager, helped them out.
When the deception of Orion—in reality, the white Martian Ma'alefa'ak—was revealed, the Team returned to Earth, taking the exiled Forager with them.
Beast Boy called a meeting of the Team and Aquaman to put forward his idea of a new team. When Aquaman objected, Beast Boy told him he did not need permission, and the five other members he had already recruited, Wonder Girl included, stepped forward. Aquaman acquiesced on the condition the new group reported to Miss Martian.
Wonder Girl was with the others at the Premiere Building when M'gann pointed out a news story about an apparent Reach attack in Brooklyn, Maine. Aquaman was responding but having little success, and the new team headed off to help.
Wonder Girl and the others worked to disable the three War Bugs. She used her lasso to pull one down from the sky, allowing Blue Beetle to deactivate the crashed ship. After Beetle disabled another ship in mid-air, Wonder Girl caught it and brought it down gently. Once the three ships were disabled, Beast Boy addressed the girls who were streaming events on their phones. He introduced the squad, before the pilots of the War Bugs were unmasked and identified as Intergang members.
Mayor Thomas Tompkins arrived on the scene and ordered Sheriff Patrick Maguire to arrest the group in accordance with the town's anti-vigilante laws. Maguire reluctantly cuffed the young heroes, but the town soon came under attack from the War Bugs' mothership, which has been summoned by an automated distress signal. The Mayor refused to let the squad deal with the situation, having called in the United States Air Force, but the squad broke free and boarded the warship. They steered it to the park so they could crash it safely before manned fighters arrived. They succeeded and all emerged from the crashed ship safely. Mayor Tompkins ordered the squad arrested once more, but this time the Sheriff refused, citing a Good Samaritan law. Beast Boy addressed the "newsgirl legion" again, and ended up naming the new team the Outsiders.
The Outsiders used a mini-drone to scope out the suspected meta-trafficking site, but the drone was quickly destroyed by some monstrous form. The squad went in finding Klarion and a Flesh monster that was clearly made up of meta-children. Wonder Girl and Static attempted to contain the creature without harming it while Beast Boy dealt with Klarion. Zatanna then arrived to help under cover of a glamour. Before Zatanna could do anything, Klarion combined Wonder Girl into the Flesh Monster, increasing its size significantly. Zatanna was soon able to separate the monster, freeing Wonder Girl. Zatanna then teleported Klarion and herself to the Tower of Fate. The Cuban military police then arrived, with one streaming events on his phone. When it became clear the MPs' leader wanted to arrest the Outsiders, they left, taking the non-Cuban metas with them.
The Outsiders and the Team worked together to thwart an attack on a UN climate summit by the Bwundan Independence Front. Though Kid Flash was injured, they succeeded with the help of the Flash, who was called in by Lex Luthor with the intention of discrediting the Outsiders and proving his oversight of the Justice League worked.
On the way back in the Bio-Ship, the Outsiders and Team discussed how they felt set up, which Lia Briggs, a meta-human they liberated from the attackers, confirmed.
The Outsiders returned from the mission and Cassie escorted Lia into the Meta-Human Youth Center. When Ed stormed out after an argument with his father over his membership of the Outsiders, Cassie and the rest of the team followed in solidarity.
Cassie arrived at the Premier Building for training. Before they could start, Cassie's mother arrived with Eduardo Dorado Sr. and Jay Garrick. Though Beast Boy had found a new mission, the three guardians refused to let their charges go. Helena had reluctantly allowed Cassie onto a covert unit but objected to the greater risks of a public team. Eventually the young heroes convinced their guardians that the importance of the Outsiders' work outweighed the risks.
Later, Cassie posted a picture of herself, Helena, Ed and Eduardo together on her 1K Wordsworth account, @WonderGirlOutsiders.
The Outsiders and Vic Stone took the Bio-Ship to the Goode World Studios lot in search of the kidnapped Halo. Vic was suspicious of a building with no web connectivity. The squad entered the building where Vic found a cloaked alien device. They were then boom tubed into an X-Pit. Wonder Girl suffered in the Pit until Vic was able to defeat Overlord in cyberspace and send them back. Cassie quickly tied up Gretchen Goode, but Goode disappeared after Vic and Beetle destroyed the alien device, with Vic boom tubing after her.
The Outsiders returned to the Premiere Building, despondent after Gretchen's apparent escape and Vic's disappearance. Two boom tubes then opened, bringing home Vic, Halo and the Team. The group celebrated the victory and inducted Vic, now Cyborg, into the Outsiders.
Cassie and Tim broke up. At some point, Cassie changed her costume.
On February 24, Wonder Girl went on a mission with the Outsiders against the Cult of the Kobra. Wonder Girl took down a helicopter, and the squad was successful in capturing Kobra and preventing the terrorists from sending a signal to brainwash people into joining the cult.
On February 25, Beast Boy went on a three-month trip to Mars, leaving Wonder Girl in charge of the Outsiders.
Wonder Girl and Windfall knocked on Gar's door to bring him on a mission to respond to Hurricane Amy. Cassie believed Weather Wizard might be involved. Gar demurred, claiming to be Javelin-lagged from his trip back from Mars.
M'gann arrived at the Premiere Building with Robotman, Cassie, Jaime and Virgil to stage an intervention for Gar. After Jaime and Virgil's comments were coldly dismissed, Cassie told Gar he couldn't speak to her-their-guys that way. She told him she was happy to continue leading the Outsiders if he didn't want to, but that she still needed her friend and mentor. Gar was unmoved by her, and everyone else. When Gar went to leave. M'gann stopped him, and reminded him that unless he was willing to leave the Outsiders and his superheroic career forever, he still had to have his annual mandatory mental health check with Black Canary.
Wonder Girl arrived with other members of the Outsiders and Justice League to respond to Dru-Zod's attack on Planet Circle, only to find the situation resolved and shocked to learn Superboy is alive.
At the Premiere Building, Wonder Girl participated in a leadership meeting about Perdita Vladek's abduction, then assured Gar he and the Outsiders would help her, once they knew where to look. She then checked in with Raptor Squad, who were pursuing a lead in Paris.
Wonder Girl and Robin became a couple after the conclusion of the Reach invasion. Seeing Wally West's death and realizing that life is short gave Wonder Girl the courage to kiss Robin. Following Robin's resignation from the Team, their relationship became quite strained, with Cassie actively trying to reconnect with him. She lamented that despite being such a great detective, he was clueless when it came to relationships.
This Wonder Girl is based on Cassie Sandsmark; Cassie is the third person to be called Wonder Girl. The first was Diana (the later Wonder Woman), the second Donna Troy, a founding member of the Teen Titans. Cassie is the daughter of Zeus and archaeologist Helena Sandsmark, though she was long unaware of her true parentage. She was granted powers by Zeus partly as a boon, and partly because he knew she was his daughter. As Wonder Girl, she joined Young Justice, and later became the leader of the Teen Titans. Following the 2011 reboot, Cassie's history has been altered, removing her direct connection to Wonder Woman.
This is Cassie's first animated appearance.
Wonder Girl was one of the few characters declared off-limits in the early production process, meaning that she could not be used during the first season. That restriction was eventually lifted.